[POWERPC] Fix bugs in the hypervisor call stats code

There were a few issues with the HCALL_STATS code:

- PURR cpu feature checks were backwards
- We iterated one entry off the end of the hcall_stats array
- Remove dead update_hcall_stats() function prototype

I noticed one thing while debugging, and that is we call H_ENTER (to set
up the MMU hashtable in early init) before we have done the cpu fixups.
This means we will execute the PURR SPR reads even on a CPU that isnt
capable of it. I wonder if we can move the CPU feature fixups earlier.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/platforms/pseries/hvCall_inst.c b/arch/powerpc/platforms/pseries/hvCall_inst.c
index 80181c4..3ddc049 100644
--- a/arch/powerpc/platforms/pseries/hvCall_inst.c
+++ b/arch/powerpc/platforms/pseries/hvCall_inst.c
@@ -34,7 +34,7 @@
  */
 static void *hc_start(struct seq_file *m, loff_t *pos)
 {
-	if ((int)*pos < HCALL_STAT_ARRAY_SIZE)
+	if ((int)*pos < (HCALL_STAT_ARRAY_SIZE-1))
 		return (void *)(unsigned long)(*pos + 1);
 
 	return NULL;
@@ -57,7 +57,7 @@
 	struct hcall_stats *hs = (struct hcall_stats *)m->private;
 
 	if (hs[h_num].num_calls) {
-		if (!cpu_has_feature(CPU_FTR_PURR))
+		if (cpu_has_feature(CPU_FTR_PURR))
 			seq_printf(m, "%lu %lu %lu %lu\n", h_num<<2,
 				   hs[h_num].num_calls,
 				   hs[h_num].tb_total,